rustdoc: `broken_intra_doc_links` triggers on link to private item

[camelid]

⚠️ Warning ⚠️

Discussion needs to take place and agreement needs to be reached before implementing this! See #83049 (comment).

---

This should succeed, but it does not.

mod foo {
    //! Look at [super::bar::baz].
}

mod bar {
    fn baz() {}
}

$ rustdoc foo.rs --document-private-items
warning: unresolved link to `super::bar::baz`
 --> foo.rs:2:18
  |
2 |     //! Look at [super::bar::baz].
  |                  ^^^^^^^^^^^^^^^ no item named `baz` in module `bar`
  |
  = note: `#[warn(broken_intra_doc_links)]` on by default

warning: 1 warning emitted

[jyn514]

Does it work without super? Inner attributes resolve relative to the module they're in.

[camelid]

Does it work without super? Inner attributes resolve relative to the module they're in.

Well, if you look at the label in the error message, the issue is not in finding bar, rather it's in finding baz within bar.

Also, using crate doesn't fix it:

warning: unresolved link to `self::bar::baz`
 --> foo.rs:2:18
  |
2 |     //! Look at [crate::bar::baz].
  |                  ^^^^^^^^^^^^^^^ no item named `baz` in module `bar`
  |
  = note: `#[warn(broken_intra_doc_links)]` on by default

warning: 1 warning emitted

Weirdly, it says self::bar::baz—it should say crate::bar::baz. Probably an unrelated bug.

[jyn514]

Weirdly, it says self::bar::baz—it should say crate::bar::baz. Probably an unrelated bug.

rust/src/librustdoc/passes/collect_intra_doc_links.rs

Lines 1038 to 1054 in acca818

	} else if path_str.starts_with("crate::") || is_lone_crate {
	use rustc_span::def_id::CRATE_DEF_INDEX;
	// HACK(jynelson): rustc_resolve thinks that `crate` is the crate currently being documented.
	// But rustdoc wants it to mean the crate this item was originally present in.
	// To work around this, remove it and resolve relative to the crate root instead.
	// HACK(jynelson)(2): If we just strip `crate::` then suddenly primitives become ambiguous
	// (consider `crate::char`). Instead, change it to `self::`. This works because 'self' is now the crate root.
	// FIXME(#78696): This doesn't always work.
	if is_lone_crate {
	path_str = "self";
	} else {
	resolved_self = format!("self::{}", &path_str["crate::".len()..]);
	path_str = &resolved_self;
	}
	module_id = DefId { krate, index: CRATE_DEF_INDEX };
	}

[jyn514]

I think the error is actually correct - baz is not visible to foo because it's in a different module. The diagnostic could be better though.

[camelid]

I think the error is actually correct - baz is not visible to foo because it's in a different module. The diagnostic could be better though.

I thought you're allowed to link to any private item from anywhere else...? I minimized this code from a project I'm working on, so there are definitely use cases.

[jyn514]

I don't think there's ever been docs on what private items you can link to. Notice that this is the "broken" lint and not the "private" lint - rustc_resolve itself is giving this error, not rustdoc, and it would need massive changes to be different (which I doubt @petrochenkov would be happy about).

[camelid]

It looks like rustc_resolve is able to give a better error:

mod foo {
    fn error() {
        super::bar::baz()
    }
}

mod bar {
    fn baz() {}
}

error[E0603]: function `baz` is private
 --> src/lib.rs:3:21
  |
3 |         super::bar::baz()
  |                     ^^^ private function
  |
note: the function `baz` is defined here
 --> src/lib.rs:8:5
  |
8 |     fn baz() {}
  |     ^^^^^^^^

I'm not 100% certain, but I think that error might be coming from here:

rust/compiler/rustc_resolve/src/lib.rs

Line 2923 in 42816d6

self.report_privacy_error(error);

rust/compiler/rustc_resolve/src/diagnostics.rs

Lines 1129 to 1133 in 42816d6

	// Print the primary message.
	let descr = get_descr(binding);
	let mut err =
	struct_span_err!(self.session, ident.span, E0603, "{} `{}` is private", descr, ident);
	err.span_label(ident.span, &format!("private {}", descr));

rust/compiler/rustc_resolve/src/imports.rs

Lines 324 to 330 in 42816d6

	if !self.is_accessible_from(binding.vis, parent_scope.module) {
	self.privacy_errors.push(PrivacyError {
	ident,
	binding,
	dedup_span: path_span,
	});
	}

Is there some way we can pick up on the fact that the item exists, but is private? Otherwise it's really confusing because the item does exist — so I end up trying to look for typos in the path, when in reality it's just that the item is private.

[jyn514]

@camelid that's #74207